Gas turbine

ABSTRACT

The invention relates to a gas turbine comprising a combustion chamber, into which fuel and combustion air are fed and caused to react, in order to produce a working fluid. The aim of the invention is to provide a particularly simple construction, which achieves a relatively high degree of efficiency for the installation. To achieve this, the inventive combustion chamber can be cooled and has a tubular structure, the combustion chamber wall being composed of coolant pipes.

CROSS REFERENCE TO RELATED APPLICATION

This application is the US National Stage of International ApplicationNo. PCT/EP2003/009703, filed Sep. 1, 2003 and claims the benefitthereof. The International Application claims the benefits of EuropeanPatent application No. 02020694.2 EP filed Sep. 13, 2002, both of theapplications are incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The invention relates to a gas turbine having a combustion chamber inwhich a supplied fuel is brought into reaction with supplied combustionair to produce a working fluid.

BACKGROUND OF THE INVENTION

Gas turbines are used in many fields to drive generators or machines. Insuch applications the energy content of a fuel is used to generate arotational movement of a turbine shaft. For this purpose the fuel iscombusted in a number of burners, with compressed air being supplied byan air compressor. Combustion of the fuel produces a high-temperatureworking fluid which is subject to high pressure. This working fluid isfed into a turbine unit connected downstream from the relevant burner,where it expands in a manner that provides work output. In thisarrangement a separate combustion chamber can be assigned to eachburner, the working fluid flowing out of the combustion chambers beingcombinable before or in the turbine unit. Alternatively, however, thegas turbine can also be designed as what is known as an annularcombustor type, in which most if not all of the burners open out into acommon, typically annular, combustion chamber.

In the design of gas turbines of this kind a particularly high level ofefficiency is normally one of the design objectives in addition to theachievable performance. Here, increased efficiency can basically beachieved for thermodynamic reasons by increasing the temperature atwhich the working fluid flows out of the combustion chamber and into theturbine unit. For this reason temperatures of around 1200 to 1500° C.are aimed at and also attained for gas turbines of this kind.

With the working fluid reaching such high temperatures, however, thecomponents and parts exposed to this medium are subject to high thermalstresses. In order nonetheless to ensure a comparatively long usefullife for the affected components, it is usually necessary to provide ameans of cooling the components in question, in particular thecombustion chamber. In order to prevent thermal deformation of thematerial which limits the useful life of the components, efforts areusually made to achieve as uniform a cooling of the components aspossible, cooling air generally being used as the coolant. In thisarrangement the cooling air is usually fed to the exterior of the innerwall of the combustion chamber via a cooling system consisting of tubesand partitions.

However, a cooling system constructed in this manner has thedisadvantage that the design of the combustion chamber and coolingsystem is very complex. In particular, the actual combustion chamberwall is assigned a separate cooling system on its exterior which in turnhas to be mounted from the outside. The process of producing acombustion chamber of this kind can therefore be very cost- andlabor-intensive, as a large number of individual parts and joiningprocesses are necessary for manufacture. This additionally results inincreased fault proneness in the manufacture and operation of the gasturbine. Maintenance and repairs are likewise rendered more difficult bythe complicated construction of the combustion chamber wall.

SUMMARY OF THE INVENTION

The object of the invention is therefore to specify a gas turbine havinga particular high efficiency while being of simple design.

This object is achieved according to the invention by the wall of thecombustion chamber being formed of coolant tubes.

The invention is based on the consideration that the gas turbine must besuitably designed to ensure a particularly high efficiency forparticularly high media temperatures. In order to minimize faultproneness, particularly reliable cooling of the thermally stressedcomponents, including the combustion chamber in particular, must beensured. This can be achieved with comparatively little complexity by,on the one hand, making the combustion chamber wall itself coolable,and, on the other hand, constructing it from shaped parts that are keptcomparatively simple and flexible. These two aspects of the combustionchamber embodiment can be adhered to by constructing the surroundingwall of the combustion chamber or the combustion chamber wall in asuitable manner from tubes, cooling air being specifically provided ascoolant which, after passing through the coolant tubes, can be suppliedto the combustion chamber as additional combustion air that has beenpreheated as a result of combustion chamber cooling.

In order to ensure particularly high strength of the combustion chamberwall, the coolant tubes are advantageously made of cast material, i.e.in other words each constituting a casting. A further advantage of thismaterial selection is that reliable heat insulation can be provided in aparticularly simple manner by suitably coating the cast material with aceramic protective layer.

In order to keep the coolant tubes particularly immune to thermalstresses and therefore particularly robust, these are advantageouslyimplemented with a trapezoidal cross-section. This cross-sectional shapeexhibits a particularly high thermal elasticity resulting in only slightthermal stresses between cold and warmer areas of the tube even in theevent of markedly differential heating of individual circumferentialsegments of the relevant tube, thereby achieving a long service life ofthe coolant tubes.

To form the combustion chamber wall and therefore also the actualcombustion chamber, the coolant tubes are expediently mounted on supportrings oriented in the circumferential direction of the combustionchamber. Through their position and form, these support rings dictatethe shape of the combustion chamber annulus to be implemented by thecoolant tubes, thereby enabling a mechanically stable combustion chamberstructure to be produced in the manner of a self-supporting structureusing only a small number of further components in addition to theactual tubes.

The coolant tubes are expediently mounted on the support rings viacooled screws, the mounting of the coolant tubes via screws allowingindividual or even a plurality of coolant tubes to be installed ordismantled in a particularly time-saving manner from the hot gas sidewhile maintaining high strength, i.e. without having to disassemble thecombustion chamber.

To ensure particularly high combustion chamber strength, the supportrings are advantageously interconnected by a number of longitudinal finsin addition to the actual coolant tubes. The longitudinal fins and thesupport rings mounted perpendicular to them together form a supportingstructure having a high degree of rigidity and strength. To provide asupporting structure of particularly high stability, the support ringsand longitudinal fins are preferably welded together so that the ringsand fins form a welded support frame.

A particularly high degree of flexibility in the shaping of thecombustion chamber, allowing in particular flow conditions in theworking fluid to be taken into account even in the combustion chamberwhile at the same time enabling a sufficient length and shape of thecoolant tubes to be ensured, can be achieved in that the coolant tubesexpediently consist of two or more tube segments interconnected in theirlongitudinal direction. The advantage of tube segmentation can bespecifically that manufacturing difficulties in producing cast ironcoolant tubes of sufficient length and appropriate shape are avoided.

In order to interconnect two consecutive segments of a coolant tube,each segment preferably has an assigned adapter piece or fitting on itsrelevant end, the adapter pieces being expediently designed for easyinterconnectability particularly in respect of their shaping. In afurther advantageous embodiment, the adapter pieces are specificallyselected such that segments can be interconnected by means of a plug andsocket connection. If the coolant tube cross-section is trapezoidal, thecross-section of the adapter piece is expediently selected such that itchanges to a circular cross-section as it approaches the joint or therelevant tube segment end. A circular end cross-section of this kindallows particularly easy machiriability for precision-fit connection tothe next tube segment.

In order to ensure effective cooling of the coolant tubes forming thecombustion chamber wall, these are advantageously impingement-cooled inan inlet area for the coolant. For this purpose, holes through which thecoolant can flow are drilled in the outside of the coolant tubes. Thecoolant can therefore impinge on the inside of the tube and ensure aparticularly intensive cooling effect in this area through intimatecontact with the tube material. In the adjacent region, the coolantflows through the tubes in the longitudinal direction, cooling them bycontact.

This cooling system has the advantage, on the one hand, that it isincorporated in the design of the combustion chamber wall and thereforeonly a small number of additional parts are required for constructingthe cooling system. On the other hand, only a small coolant pressureloss occurs precisely due to the comparatively straight-line outflow ofthe coolant. The advantage of this is that it facilitates a high degreeof turbine efficiency even on the coolant side.

To ensure a particularly high overall efficiency of the gas turbine, theheat input to the coolant is advantageously recovered for the actualenergy conversion process in the gas turbine. For this purpose thecooling air used as coolant and which has been heated during the coolingprocess is advantageously injected into the combustion chamber, thepre-heated cooling air being able to be used as the only combustion airor as additional combustion air.

In order to feed the outflowing coolant to the combustion process in thecombustion chamber for this purpose, each coolant tube is preferablyconnected on the output side to a collecting chamber which for its partis disposed upstream of the combustion chamber on the air side. Via thischamber, the coolant can be mixed with the remaining compressor massflow by a throttling device and fed to the combustion process.

Compensation of the flow conditions is achievable to an particulardegree by assigning a collecting chamber of this kind to each burner,the design basis being such that the same quantity of cooling air orcoolant is fed to each collecting chamber. To this end each burner ispreferably assigned a collecting chamber, each connecting chamber beingconnected to the same number of coolant tubes. The particular advantageof this arrangement is that each burner is fed approximately the sameamount of returned cooling air. Just by implementing the combustionchamber as an annular combustor ensures that a particularly homogenouscombustion process is thereby produced in the combustion chamber.

The advantages achieved with the invention are specifically thatparticularly reliable combustion chamber cooling of simple design ismade possible by implementing the combustion chamber wall as a pluralityof interconnected coolant tubes provided for the through-flow ofcoolant, specifically cooling air. The integration of the coolant tubesin a self-supporting combustion chamber structure, in particular bymeans of the support rings, allows comparatively easy interchangeabilityof even individual maintenance-requiring tubes, a simple means ofreplacing combustion chamber structures in existing gas turbines alsobeing provided, however, because of the flexibility achievable via thetubular design. Moreover, the tubular combustion chamber structure iscomparatively stable and immune to vibrations of the combustion chamberwall, as the coolant tubes lend rigidity and strength to the annulus.The basic flexibility in terms of shaping and component selectionachieved by constructing the combustion chamber wall from tube elementsadditionally enables probes or monitoring sensors for monitoring and/ordiagnostics of the actual combustion process in the combustion chamberto be mounted, particularly by selectively using specifically modifiedtubes which allow, for example, suitable probes to be fed through fromthe outside to the inside of the combustion chamber.

BRIEF DESCDRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is now explained in greaterdetail with reference to the accompanying drawings in which:

FIG. 1 shows a half-section through a gas turbine,

FIG. 2 shows in longitudinal section a segment of the combustion chamberof the gas turbine according to FIG. 1, and

FIG. 3 a to c each show in cross-section a detail of the combustionchamber wall according to FIG. 2.

The same parts are denoted by the same reference characters in all theFigures.

DETAILED DESCRIPTION OF THE INVENTION

The gas turbine 1 according to FIG. 1 has a compressor 2 for combustionair, a combustion chamber 4 as well as a turbine 6 for driving thecompressor and a generator (not shown) or a machine. For this purposethe turbine 6 and the compressor 2 are disposed on a common turbineshaft 8, also referred to as a turbine rotor, to which the generator orthe driven machine are connected and which is pivotally mounted aboutits central axis 9.

The combustion chamber 4 implemented in the form of an annular combustoris equipped with a number of burners 10 for combusting a liquid orgaseous fuel. It is additionally provided with heat shield elements (notshown in greater detail) on its inner wall.

The turbine 6 has a number of rotating blades 12 connected to theturbine shaft 8. These rotor blades 12 are disposed in a ring shapedmanner on the turbine shaft 8, thereby forming a number of rotor bladerows. The turbine 6 additionally comprises a number of fixed guide vanes14 which are likewise mounted in a ring shaped manner on an inner casing16 of the turbine 6, forming guide vane rows. The rotor blades 12 areused to drive the turbine shaft 8 by pulse transmission from the workingfluid M flowing through the turbine 6, whereas the guide vanes 14 serveto direct the flow of the working fluid M between two consecutive rotorblades rows or rotor blade rings viewed in the direction of flow of theworking fluid M, a consecutive pair from a ring of guide vanes 14 orguide vane row and from a ring of rotor blades 12 or rotor blade rowalso being referred to as a turbine stage.

Each guide vane 14 has a platform 18, also referred to as a blade root,which is disposed as a wall element for fixing the relevant guide vane14 on the inner casing 16 of the turbine 6, said platform 18 being acomparatively heavily thermally stressed component forming the externalboundary of a hot gas channel for the working fluid M flowing throughthe turbine 6. Each rotor blade 12 is similarly mounted on the turbineshaft 8 via a platform 20 also referred to as a blade root.

A guide ring 21 is disposed on the inner casing 16 of the turbine 6between the spaced-apart platforms 18 of the rotor blades 14 of twoadjacent rotor blade rows in each case, the outer surface of each guidering 21 likewise being exposed to the hot working fluid M flowingthrough the turbine 6 and being separated from the outer end 22 of theopposite rotor blade 12 by a gap in the radial direction, the guiderings 21 disposed between adjacent rows of guide vanes being used inparticular as cover elements which protect the inner wall 16 or otherintegral parts of the casing from thermal overstressing by the hotworking fluid M flowing through the turbine 6.

To achieve a comparatively high level of efficiency, the gas turbine 1is designed for a comparatively high exit temperature of the workingfluid M leaving the combustion chamber 4 of around 1200 to 1500° C. Inorder also to ensure a long lifetime or operating life of the gasturbine 1, its main components such as the combustion chamber 4 inparticular are implemented in a coolable manner whereby, in order toensure a reliable and sufficient supply of cooling air to the combustionchamber wall 23 of the combustion chamber 4 as coolant K, the combustionchamber wall 23 is of tubular construction comprising a plurality ofcoolant tubes 24 interconnected in a gas-tight manner to form saidcombustion chamber wall 23.

In the exemplary embodiment the combustion chamber 4 is designed as aso-called annular combustor, wherein a plurality of burners 10 arrangedin the circumferential direction around the turbine shaft 8 open outinto a common combustion chamber space. For this purpose the combustionchamber 4 is implemented in its totality as an annular structure whichis positioned around the turbine shaft 8. To further clarify theembodiment of the combustion chamber wall 23, FIG. 2 shows inlongitudinal section a segment of the combustion chamber 4 whichcontinues in a toroidal manner around the turbine shaft 8 to form thecombustion chamber 4.

As shown in the diagram according to FIG. 2, the combustion chamber 4has an initial or inflow section into which the outlet of the respectiveassigned burner 10 opens at the end. Viewed in the direction of flow ofthe working fluid M, the cross-section of the combustion chamber 4 thennarrows, with account being taken of the resulting flow profile of theworking fluid M in this area. On the outlet side, the combustion chamber4 exhibits in its longitudinal cross-section a curvature which favorsthe outward flow of the working fluid M from the combustion chamber 4resulting in a particularly high pulse and energy transmission to thefollowing first row of rotor blades seen from the flow side.

As shown in the diagram according to FIG. 2, the combustion chamber wall23 is formed, both in the external area of the combustion chamber 4 andin its inner area, from coolant tubes 24 which are oriented with theirlongitudinal axis essentially parallel to the flow direction of theworking fluid M inside the combustion chamber 4, the coolant tubes 24being made of cast material which has been suitably selectedspecifically with regard to a particularly high mechanical and thermalstrength of said coolant tubes.

In order to provide particularly high flexibility in the shaping of thecombustion chamber 4 formed from the coolant tubes 24 to suit therequired flow conditions of the working fluid M, in the exemplaryembodiment each coolant tube 24 is constituted by a suitable combinationof a plurality of consecutive tube segments 26, the type and number ofsaid tube segments 26 being selected in such a way that, on the onehand, a particularly high mechanical strength of each individual tubesegment 26 is ensured with regard to the length and shaping of each tubesegment 26 and with regard to the cast material used, the shaping on theother hand being suitably selected in each case taking into account therequired flow path for the working fluid M. The comparatively sharplocal curvature possibly required can be provided in a particularlysimple and reliable manner by the segmentation of the coolant tubes 24.

The coolant tubes 24 are additionally designed to be particularly strongspecifically with regard to locally varying thermal loading and theresulting thermal stresses. For this purpose, the coolant tubes 24 andin particular the tube segments 26 forming them are of essentiallytrapezoidal cross-section, as shown for the central piece of a tubesegment 26 in FIG. 3 a, the coolant tubes 24 having a comparativelylonger inner side 28 and a comparatively shorter outer side 30 incross-section to form the toroidal, intrinsically curved structure ofthe combustion chamber 4. To seal the interspaces between adjacentcoolant tubes 24, a suitable seal, e.g. a brush seal 32, is provided soas to produce a gas-tight and enclosed combustion chamber 4 by means ofa suitable combination of coolant tubes 24.

The trapezoidal embodiment of the tube cross-sections favors inparticular an intrinsically planar embodiment of the structureobtainable by joining together adjacent coolant tubes 24, so that theenclosed implementation of the combustion chamber 4 can be achieved in acomparatively simple manner.

For the segmented construction of the coolant tubes 24, the connectionof two consecutive tube segments 26 of each coolant tube 24 on thecoolant side has been kept particularly simple, particularly with regardto assembly and maintenance purposes. To achieve this, consecutive tubesegments 26 of a coolant tube 24 are interconnected via an assignedadapter piece 34. To facilitate assembly of consecutive tube segments26, each tube segment 26 is of essentially circular cross-section in itsend areas to form the relevant adapter piece 34, as shown in FIG. 3 b.By producing the coolant tubes 24 from cast material, the shaping of therelevant adapter piece 34 to suit the relevant tube segment 26 ispossible in a comparatively simple manner, there being provided in theadapter area a continuous transition from the actually trapezoidalcross-section of the relevant tube segment 26 to the circularcross-section provided at the end. As shown in FIG. 2, the relevantadapter pieces 34 are displaced into the outer area of the combustionchamber 4 with respect to their central line and in comparison to thecentral pieces of the relevant tube segments 26, so that an essentiallycontinuous smooth surface can be provided using suitable seal strips orplates in the inner walls of the combustion chamber 4.

To form the combustion chamber 4 as an integral, self-supportingstructure, the coolant tubes 24 are mounted on a plurality of commonsupport rings 36 which enclose the combustion chamber 4 formed from theactual coolant tubes 24 at a suitably selected spacing viewed in thelongitudinal direction or in the flow direction of the working fluid M.The relevant coolant tubes 24 or the tube segments 26 forming them aremounted on the support rings 36 via coolable screws 38, as shown in theembodiment according to FIG. 3 c. For further stiffening and mechanicalfixing of the self-supporting structure forming the combustion chamber4, the support rings 36 are interconnected by longitudinal finsessentially oriented in the longitudinal direction or in the flowdirection of the working fluid M.

The tubular design of the combustion chamber 4 means that acomparatively large amount of cooling air can be applied to thecombustion chamber wall 23 as coolant K with only comparatively lowpressure losses. In order enable the heating of the coolant K flowingthrough the coolant tubes 24 for cooling the combustion chamber wall 23to be used for the actual combustion process in a manner promotingthermodynamic efficiency, provision is made for the coolant K issuingfrom the coolant tubes 24 to be injected into the combustion chamber 4as the sole or additional combustion air. For this purpose provision ismade for supplying the coolant K to the coolant tubes 24 at their endsassigned to the outlet of the combustion chamber 4, where the coolant Kis supplied to the coolant tubes 24 via suitable inflow ports 42, asshown in FIG. 2, said inflow ports 42 being positioned in respect oftheir spatial orientation in such a way that impingement cooling of therelevant tube segment 26 initially takes place in the outlet area of thecombustion chamber 4 by means of the cooling air flowing in as coolantK. Deflection of the coolant K then takes place inside the relevant tubesegment 26, and the coolant K then flows through the relevant coolanttube 24 in its longitudinal direction, cooling taking place throughcontact of the coolant K with the relevant tube walls.

In the manner of a counter-flow to the actual working medium M, thecoolant K therefore flows inside the coolant tubes 24 from the outletarea of the combustion chamber 4 to its inflow area in which therelevant burner 10 is also disposed. In this area the coolant K nowheated or pre-heated by the continuous cooling of the relevant coolanttube 24 flows out of the coolant tubes 24 and is then assigned to asubordinate collecting chamber 46. The coolant tubes 24 are connectedvia said collecting chamber 46 to the assigned burner 10 on the outputside so that the coolant K flowing out of the coolant tubes 24 can beused as combustion air in the relevant burner 10. Depending on thedesign of the gas turbine 1, the feeding of the relevant burner 10 withcombustion air can be provided exclusively via the coolant K flowing outof the coolant tubes 24 or also using in some cases additionallyrequired further combustion air supplied from an external source.

By the very embodiment of the combustion chamber 4 as an annularcombustor, a maximally symmetrical arrangement of the burners 10 andconsequently a maximally symmetrical adjustment of the flow conditionswithin the combustion chamber 4 is ordinarily advantageous. For the gasturbine 1, this basic principle is also taken into account on thecoolant side, specifically in that the same number of coolant tubes 24is assigned to each burner 10 on the combustion air side.

1-9. (canceled)
 10. A gas turbine, comprising: a combustion chamberhaving a combustion chamber wall; and coolant tubes forming thecombustion chamber wall, wherein each coolant tube is comprised of aplurality of tube segments with consecutive tube segments of a coolanttube being interconnected via an assigned adapter piece and the adapterpieces are implemented so that the tube segments can be connected by aplug and socket connection.
 11. The gas turbine according to claim 10,wherein the coolant tubes are made of cast material.
 12. The gas turbineaccording to claim 10, wherein the coolant tubes have a trapezoidalcross-section.
 13. The gas turbine according to claim 12, wherein thecross-section of the adapter pieces transition to a circularcross-section near a relevant joint.
 14. The gas turbine according toclaim 10, wherein the coolant tubes are mounted on a plurality of commonsupport rings.
 15. The gas turbine according to claim 14, wherein thecoolant tubes are mounted on the support rings via coolable screws. 16.The gas turbine according to claim 14, wherein the support rings areinterconnected by a plurality of longitudinal fins to form a supportingstructure.
 17. The gas turbine according to claim 10, wherein eachcoolant tube is connected on an output side to a collecting chamberthrough which an outflowing coolant is fed to a burner.
 18. The gasturbine according to claim 17, wherein each burner is assigned acollecting chamber and each collecting chamber is connected to the samenumber of coolant tubes.
 19. A gas turbine combustion chamber,comprising: a combustion chamber wall; and coolant tubes forming thecombustion chamber wall, wherein each coolant tube is comprised of aplurality of tube segments with consecutive tube segments of a coolanttube being interconnected via an assigned adapter piece and the adapterpieces are implemented so that the tube segments can be connected by aplug and socket connection.
 20. The gas turbine combustion chamberaccording to claim 19, wherein the coolant tubes are mounted on aplurality of common support rings.
 21. The gas turbine combustionchamber according to claim 19, wherein the coolant tubes are mounted onthe support rings via coolable screws.
 22. The gas turbine combustionchamber according to claim 19, wherein the support rings areinterconnected by a plurality of longitudinal fins to form a supportingstructure.